1. Field of the Invention
The present invention relates to a composition for removing a copper (Cu)-compatible resist, and more particularly, to a composition for removing a copper-compatible resist without corrosion of copper.
2. Discussion of the Related Art
In general, a low resistance copper line is commonly used as an array line of an array substrate for a liquid crystal display (LCD) device, or in a circuit line of a semiconductor device to prevent resistance-capacitance (RC) delay. A copper layer for the copper line is formed through a chemical vapor deposition (CVD) method, an atomic layer deposition (ALD) method, an electroless deposition method, or an electroplating method as an electrochemical deposition method. The copper line is commonly formed using a photolithographic process incorporating fine pattern technology. The photolithographic process is commonly used for fabricating semiconductor devices such as large scale integrated (LSI) circuits, very large scale integrated (VLSI) circuits, and display devices including an LCD device and a plasma panel display (PDP) device.
FIG. 1 is a perspective view of a liquid crystal display device using a copper line according to the related art.
In FIG. 1, a liquid crystal display (LCD) device 11 includes an upper substrate 5, a lower substrate 10, and a liquid crystal layer 9 interposed between the upper and lower substrates 5 and 10. The upper substrate 5 includes a color filter layer 7, a black matrix 6, and a common electrode 18. The lower substrate 10 includes a pixel electrode 17 formed at a pixel region “P,” a switching element “T,” and an array line. Thin film transistors (TFTs) “T” as a switching element are disposed in a matrix configuration, and gate and data lines 14 and 22 are connected to each of the TFTs “T.” The pixel region “P” is defined by the gate and data lines 14 and 22, and the transparent pixel electrode 17 is formed at the pixel region “P.” The pixel electrode 17 and the common electrode 18 are made of a transparent conductive metal such as indium-tin-oxide (ITO) and indium-zinc-oxide (IZO). The LCD device 11 is driven by utilizing an electro-optical effect of the liquid crystal layer 9. Accordingly, the gate line 14 should be made of a low resistance material such as copper (Cu) and copper/titanium (Cu/Ti).
FIG. 2 is a schematic cross-sectional view of an array substrate for a liquid crystal display device according to the related art.
In FIG. 2, a gate electrode 30 and a gate line 14 (of FIG. 1) are formed on a substrate 10 by depositing and patterning a conductive metallic material such as aluminum (Al), chromium (Cr), molybdenum (Mo) and copper (Cu). A first insulating layer (a gate insulating layer) 32 is formed on the gate electrode 30 and the gate line 14 (of FIG. 1). An active layer 34 of intrinsic amorphous silicon (a-Si:H) and an ohmic contact layer 36 of impurity-doped amorphous silicon (n+or p+ a-Si:H) are formed on the first insulating layer 32 over the gate electrode 30. Source and drain electrodes 38 and 40 are formed on the ohmic contact layer 36 by depositing and patterning a conductive metallic material such as aluminum (Al), chromium (Cr), molybdenum (Mo) and copper (Cu). At the same time, a data line 22 connected to the source electrode 38 is formed on the first insulating layer 32. A second insulating layer (a passivation layer) 42 is formed on the source and drain electrodes 38 and 40, and the data line 22. A transparent pixel electrode 17 connected to the drain electrode 40 is formed on the second insulating layer 42.
Array lines such as the gate line 14 (of FIG. 1) and the data line 22 can be made of Cu having a low resistance. The Cu line can be used as a metal line of a semiconductor device.
FIGS. 3A to 3E are cross-sectional views showing a photolithographic process of a copper line for a liquid crystal display device or a semiconductor device according to the related art.
In FIG. 3A, a metal layer 62 is formed on a substrate 60 by depositing a metallic material for a metal line. A semiconductor substrate (a wafer) or a glass substrate can be used as the substrate 60. Next, a photoresist (PR) layer 64 of positive or negative type is formed on the metal layer 62. For example, a positive type PR layer will be illustrated in FIGS. 3A to 3E. Even though the PR layer 64 may be formed on an entire or a predetermined region of the substrate 60, the PR layer 64 is generally formed on the entire region of the substrate 60.
In FIG. 3B, a photo mask 66 having a predetermined pattern is disposed over the PR layer 64 of the substrate 60. Next, an exposure process is performed, wherein light “L” such as an ultra violet (UV) ray and an X ray is irradiated onto the photo mask 66. The photo mask 66 includes a transmitting portion “E” and a shielding portion “F,” wherein the light passing through the transmitting portion “E” transforms the PR layer 64. Accordingly, the PR layer 64 includes a first portion “C” where a material property of the PR layer 64 is maintained and a second portion “D” where a material property of the PR layer 64 is transformed. Since the PR layer 64 is potentially patterned according to the photo mask 66, this pattern of the PR layer 64 is referred to as a latent image.
In FIG. 3C, the PR layer 64 (of FIG. 3B) having the latent image is developed to form a resist pattern 65 that corresponds to the photo mask 66 (of FIG. 3B). Specifically, the first portion “C” (of FIG. 3B) where the light “L” (of FIG. 3B) is not irradiated remains to cover the metal layer 62 and the second portion “D” (of FIG. 3B) where the light “L” (of FIG. 3B) is irradiated is eliminated to expose the metal layer 62.
In FIG. 3D, the metal layer 62 (of FIG. 3C) is etched using the resist pattern 65 as an etching mask, whereby a metal line 68 of a specific shape is formed on the substrate 60.
In FIG. 3E, the resist pattern 65 (of FIG. 3D) is eliminated, and the metal line 68 of the specific shape is exposed.
However, the metal line of copper may be easily corroded by conventional solvents used for removing the resist pattern. Accordingly, an advantage of the present invention is to eliminate the resist pattern 65 on the metal line 68 without corrosion of the metal line 68. Solvent compositions that include a corrosion inhibitor for preventing corrosion of copper may be used, as demonstrated by U.S. Pat. Nos. 5,417,877 and 5,556,482, which are hereby incorporated by references for all purposes as if fully set forth herein. The corrosion inhibitors include monoethanolamine (MEA) as a preferred amine. In addition, a specific amount of corrosion inhibitor is required so that a removing property of the inhibitor is not degraded.
FIG. 4 is a scanning electron microscope (SEM) image showing a corrosion state of a copper line when a solvent composition including conventional amine is used.
In FIG. 4, when a resist pattern is eliminated by using a solvent composition including conventional amine, corrosion of a copper line is not prevented. As a result, the copper line is also eliminated due to a galvanic effect, and a fragment of the copper line is laid on a glass substrate. Accordingly, reliability of the metal line is reduced due to such a defect.
Solvent compositions that include an organic acid for eliminating a resist pattern may be used, as demonstrated by U.S. Pat. No. 4,242,218, which is hereby incorporated by reference for all purposes as if fully set forth herein. A solvent composition of petroleum compound having 1–14 carbon chain classified into alkylsulfonic acid and alkylallyl is suggested. Dodecylbenzenesulfonic acid and toluenesulfonic acid are disclosed as arylsulfonic acid. However, the solvent compound having an organic acid causes severe corrosion of a copper line when a corrosion inhibitor is not added.